Since this is my first time building within the “steampunk” genre, I thought I’d take it easy and only make this half-steampunk. At first I didn’t know what category to put this under, but I decided to put it under steampunk because that’s what most of the minifigs are. Anyways, here’s my attempt at a backstory (which I didn’t put too much thought into):
In a totally original, fictional world, an advanced spaceship is accidentally sent to the past along with a robot. With only the front half being left intact, a very wealthy businessman commissions the rear half to be rebuilt from scratch. He then hires a team to use the newly-christened Duplicitous Cockatrice to combat the evil lord of the Long-Necked Frog People.
I know the ship has a weird name, but it’s supposed to. Remember, your ideas are always welcome. Maybe I’ll build a ship for the lord of the Long-Necked Frog People, but probably not. By the way, my favorite creation was unfortunately pushed off of my main page today because I posted this. Go check it out while you’re here.
Overall side view. The next few pictures are of all the minifigs involved with this MOC.

Captain.
TASK: Giving orders, being in charge of missions

Rich guy who owns the second half of the ship.
TASK: Managing money, financing expeditions

Magician.
TASK: Magic

Robot, who came from the future with the front half of the ship.
TASK: Helping the pilot operate the front half, being an all-around crew member

Firearms expert.
TASK: Shooting guns, operating cannons

Pilot.
TASK: Controlling the front half of the ship

Archer #1.
TASK: Shooting things

Archer #2.
TASK: Shooting things

Kid.
TASK: Tagging along

Monkey.
TASK: Causing trouble

Lord of the Long-Necked Frog People and his two ghost-minions. They wield oversized axes and have heads that glow in the dark.
TASK: Antagonists

General view of the front half. The quarter-saucer pieces from the Mars Mission sets are the same size as the quarter-saucer bases that I got from the big Arachnoid Insectoids set, so I put them together to make an airtight half-saucer for the front. I would link to this stuff on the BrickLink catalog so you can have an idea of what I'm talking about, but apparently deep links don't work anymore.

The pilot at his station. He is using a phone that connects to another one used by the captain at his station in the rear half.

Although it’s probably hard to tell since black LEGO® creations do not show up very well on camera (at least not on my camera, which is only supposed to be used for taking pictures of your face), I took the roof off of the front section for a view of the interior. There’s not much in here except for the pilot, the archers, and the kid who is studying things with his magnifying glass.

The pilot’s station.

One of the archers at his station. The front half has retractable landing gear and the back half has three non-retractable legs for landing gear.

Underside. You can see all of the landing gear and takeoff jets.

The big cylinder on the deck of the rear half is the boiler. I know it’s a bad place to put a boiler, but it wouldn’t fit anywhere else. You can also see the three engines on the roof of the front section. These super-futuristic engines are thought-activated and powered by pure awesomeness.

General view of the back section. You can see the captain on the phone with the pilot. I think I have a ship’s wheel piece somewhere in my collection, but I couldn’t find it after spending a really long time searching, so I gave up and used a gear instead.

Here’s a good shot of the propellors and one of the bombs, which is attached to the ship magnetically.

One of the bombs by itself.

Rear view.

I took the roof off of this part to get a good shot of the rich guy studying the map. He likes to sit right next to the treasure. The captain’s sword is barely visible hanging on the wall behind him.

A fight to the death!

Response to Shannon Young:Honestly, it was designed that way from the beginning. And just so everyone knows, Lee Jones reviewed this, too, but I had to delete it because it was somehow changed into my name. If I remember correctly, he said something about how it looks like Jabba's sail barge rear-ended a space cruiser.

Quoting sam tenney
prety cool.how did you get the idea?good job.how many pepole can be on the ship?

Wow, it's been a while since this ancient thing got a comment! Believe it or not, it's still together and I intend to take better photos of it soon (i.e. whenever I can get a tripod for my camera) because it's actually one of my personal favorite MOCs. I don't even remember where I got the idea for it, and kind of a lot of people (minifigs) can be on it.

Wow, that's cool and weird at the same time. I like the name, story, crew, and the total weirdness ("evil lord of the Long Necked Frog People")! Check out my stuff if you have a chance, and maybe review something.

Ha, this is great. I love the steampunk/Alien tech melding. You did a wonderful job on the crew and vilians. Added to that the subtitles made me luagh (something many TV shows have failed at miserably.) But then, I'm a nerd so it would only be logical for something this cool to make me luagh. POST SCRIPT: Sorry I never thanked you for those reviews.

Say "Duplicitous Cockatrice" five times fast! Very interesting, absolutely unique ship. And a monkey on the crew, how do you beat that? I like the story explaining the cobbled-together look, but I want to know the truth: was it designed that way from the get-go, or did you have two separate projects going and decided at some point that they were going to be mashed together?